What Causes A Small Lump On The Bottom Of Testicle?

I am a 38 year old white male. I recently found a very small hard bump on my left testicle. It is about the size of a pin head. It is located on the bottom front area and it is attached to my testicle. It isn t painful. I wouldn t consider it a lump because it is round and so small. What could this be? Should I just monitor it over a few weeks to see if it changes size or should I go to a doctor now. It is so small I will probably have to show him where to look to find it. If it was a tumor, how fast should it grow? I think it is probably nothing, but just wanted to ask. Thanks.